Drug interactions
Lapatinib + Tolvaptan
Severity: Major
Lapatinib and Tolvaptan: major interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Lapatinib inhibits CYP3A4 and P-glycoprotein and may increase tolvaptan exposure. This can result in excessive diuresis, dehydration and too rapid correction of sodium.
What this interaction means in plain words
Lapatinib and Tolvaptan can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for.
Lapatinib belongs to Oncology; Tolvaptan belongs to Endocrine.
Why it happens
Inhibition of CYP3A4 and P-glycoprotein by lapatinib reduces tolvaptan clearance.
What to do
Avoid if possible, or lower the tolvaptan dose and monitor serum sodium and volume status.
What to ask your pharmacist
- Does the benefit of taking both outweigh the risk in my case?
- Do I need any blood test, ECG or other check while on both?
- What early warning signs should I watch for, and what should I do if they appear?
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Other interactions of Lapatinib
- Dofetilide + Lapatinib Contraindicated
- Ibutilide + Lapatinib Contraindicated
- Lapatinib + Pimozide Contraindicated
- Lapatinib + Saquinavir Contraindicated
- Lapatinib + Thioridazine Contraindicated
- Adagrasib + Lapatinib Major
Other interactions of Tolvaptan
- Atazanavir + Tolvaptan Contraindicated
- Ceritinib + Tolvaptan Contraindicated
- Cobicistat + Tolvaptan Contraindicated
- Conivaptan + Tolvaptan Contraindicated
- Darunavir + Tolvaptan Contraindicated
- Idelalisib + Tolvaptan Contraindicated
Frequently asked questions
Can I take Lapatinib with Tolvaptan?
MediHelp rates the interaction as major. Lapatinib and Tolvaptan can interact in a way that may be serious. Using them together is sometimes necessary, but it needs a deliberate decision by the prescriber, a plan for monitoring, and clear advice on the warning signs to watch for. Lapatinib inhibits CYP3A4 and P-glycoprotein and may increase tolvaptan exposure. This can result in excessive diuresis, dehydration and too rapid correction of sodium.
How serious is the interaction between Lapatinib and Tolvaptan?
MediHelp rates it major, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid if possible, or lower the tolvaptan dose and monitor serum sodium and volume status.
What other medicines interact with Lapatinib?
MediHelp also lists interactions of Lapatinib with, for example, Dofetilide, Ibutilide, Pimozide. The full list is on the Lapatinib page.
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